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The two-layer nanotubes consisted of carbon atoms on the outside layer and silicon atoms on the inside layer (CNT@SiNT) show a series of diversity in the shape transitions, for instance transforming from a circle through an oval to a rectangle. In this paper, we investigate this geometric change from three perspectives. In the first aspect, we stationary time, followed by quantize in the three-dimensional Z-axis of nanotubes. In the second aspect, we stationary Z-axis, followed by quantize in the time. Finally, we tracked distance of nanotubes flattest section and roundest section. At the stationary time, the overall image of different Z-axis distance distributions is similar to a plan view of multiple ice creams, regardless of whether CNT or SiNT are on the same Z-axis, their slice plans are circle or rectangle of the projection of the Z-axis section on the XOY plane. In the stationary Z-axis, the nanotubes periodically change from a circle to an oval, and then from an oval to a rectangle at different times. Most remarkably, the distance value of deformation which we track the flattest and roundest is a constant value, and in the same distance period, there is only one roundest circle and one longest rectangle at different section and different time. The geometric analysis provided theoretical reference for the preparation of various devices and semiconductor nano-heterojunctions.

To understand the photoluminescence mechanisms and optimize the design of Mg 2 Si-based light-emitting devices, Mg 2 Si films were fabricated on silicon (111) and glass substrates by magnetron sputtering technique, and the influences of different substrates on the photoelectric properties of Mg 2 Si films were investigated systematically. The crystal structure, cross-sectional morphology, composition ratios and temperature-dependent photoluminescence (PL) of the Mg 2 Si films were examined using X-ray diffraction (XRD), Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and PL measurement system, respectively. XRD results indicate that the Mg 2 Si film on Si (111) displays polycrystalline structure, whereas Mg 2 Si film on glass substrate is of like-monocrystalline structure.SEM results show that Mg 2 Si film on glass substrate is very compact with a typical dense columnar structure, and the film on Si substrate represents slight delamination phenomenon. EDS results suggest that the stoichiometry of Mg and Si is approximately 2:1. Photoluminescence (PL) of Mg 2 Si films was observed for the first time. The PL emission wavelengths of Mg 2 Si are almost independence on temperature in the range of 77–300 K. The PL intensity decreases gradually with increasing temperature. The PL intensity of Mg 2 Si films on glass substrate is much larger than that of Mg 2 Si film on Si (111) substrate. The activation energy of 18 meV is determined from the quenching of major luminescence peak(1342 nm) as a function of temperature in the Mg 2 Si film grown on Si (111) substrate, which is much smaller than that deduced in the sample grown on glass substrate (about 25meV). The small activation energy can be attributed to the additional nonradiative centers originated from relatively poor crystal quality.The physical mechanism responsible for the measured ∼1342 nm and other three longer wavelengths emissions may be respectively result from strong Mg i donor level to valence band transitions and other defect-related radiative recombination occurred in the Mg 2 Si films.

Melting refers to the phase transition from solid to liquid, which is a common physical phenomenon in nature. It is also a phase transformation process that the materials such as metals and semiconductors need to undergo in the process. It is closely related to the preparation and performance of materials. At present, it is difficult to trace the microstructure of the melting process, and computer simulation can get a lot of microstructure information of the melting process, which can well explain how the orderly arrangement of crystals becomes random liquid phase structure in the melting process. For the ternary semiconductor alloy In x Ga1 - x As, it has important application value in microelectronics and optoelectronic devices, because it can adjust its electrical parameters and optical band gap in a wide range composition. So the research of alloy structure has been paid more and more attentions for the ternary semiconductor. It is generally known that the macroscopic properties of the materials are mainly determined by their microstructures. However, most studies on the melting process are based on the dynamics, but the mechanism of the evolution of the microstructure during the melting process is lacking. Therefore, it is of great significance to study the evolution of microstructures during the melting process of InGaAs crystals in the development of novel optoelectronic materials and devices. At present, it is still difficult in the experiment to obtain the structural details of InGaAs system during the melting process. Molecular dynamics simulation is an efficient tool especially for such process. In this paper, the melting process of the ideal InGaAs crystal is simulated by using the molecular dynamics method, and the Tersoff potential function of the In x Ga1 - x As covalent bond system, which has been proved to be suitable for the simulation of complex structures. The structural evolution of the solid-liquid phase transition process was analyzed by using the radial distribution function, angular distribution function, coordination numbers and 3D visualization. From the results of our simulation, we find that the microstructures of the InGaAs phase change greatly during the solid-liquid phase transition, especially in the first-order phase transition. It shows significant variations in the average atomic energy and specific volume, the radial distribution function, angular distribution functions, coordination numbers and atomic cross-sections, local atomic distributions, and diamond structure analysis. In the melting process, covalent bonds the InGaAs atoms are broken, and the system changes from the four coordinated structure into the three coordinated structure. For the dominant three coordinated structure and a small amount of four coordinated structures, the three coordinated structure is connected with the three coordinated structure, and the three coordinated structure interpenetrated the four coordinated structure to form a disordered topological structure.

In this study, the epitaxial growth of the full-composition-graded AlxGa1-xN films has been demonstrated on the sapphire substrates by using metalorganic chemical vapor deposition (MOCVD). The aluminum composition in the AlxGa1-xN films has been precisely controlled from 0 to 100%, as confirmed by X-ray diffraction and energy-dispersive spectroscopy analyses. The pseudo-periodic AlxGa1-xN/AlyGa1-yN structures are spontaneously formed during the initial growth of the graded AlGaN layer, which facilitate the strain relaxation. In addition, the behavior of the bending dislocations has been investigated in detail, and the threading dislocation bending along the growth direction is noted to relax the strain further.

Ternary photocatalyst, reduced graphene oxide-ZnFe 2 O 4 -polyaniline (RZP), has been successfully developed by the in-situ polymerization of aniline on the reduced graphene oxide-ZnFe 2 O 4 (RG/ZF) surface for sewage purification. The SEM, TEM and STEM images suggest that PANI has coated the RG/ZF composite well. The XRD, TG-DTG and FT-IR analysis confirm that there are some interactions between RG/ZF composite and PANI. Importantly, the decontamination performance of RZP composites has been investigated using RhB as a model organic in view of adsorption and photocatalysis. On one hand, thermodynamic researches indicate that the adsorption behaviors of RZP composites conform to the Langmuir model, and their adsorption mechanism can be well described by the second-order kinetic model. On the other hand, RZP composites with different mass ratios of PANI to RG/ZF ( m P/RZ ) present a better photocatalytic activity than that of RG/ZF composites, and their photocatalytic behaviors under different pH could be described by the first-order kinetic model. Furthermore, it can be observed that the RZP composite with m P/RZ = 0.4 has the excellent photocatalytic activity and photocatalytic stability under pH = 1. Finally, the possible photocatalytic degradation mechanisms of the RZP composite on RhB have been discussed. These results can unveil that the prepared RZP photocatalyst is very promising for application in water purification.

Magnetic reduced graphene oxide-ZnFe 2 O 4 composites (RG/ZF) were successfully prepared through a simple chemical co-precipitation method, and their composition, structure, and morphology were characterized by XRD, Raman, SEM, TEM and STEM. These results indicated that the as-prepared RGO with some defects and few reactive groups containing oxygen possessed the few-layered crystal structure, and the ZnFe 2 O 4 nanoparticles with spinel structure were homogeneously dispersed in the interlayer of graphene sheets. The interactions between two components had been investigated by TG and FT-IR. Importantly, kinetic researches indicated that the adsorption behavior of RG/ZF composite could be well described by the second-order kinetic model. Their adsorption effect on RhB conformed to the Langmuir model and belonged to the monolayer chemical adsorption, which were illustrated by thermodynamic experiment. In addition, RG/ZF composites with different mass ratio of RG to ZF ( m RG/ZF ) presented good photocatalytic activity, and their photocatalytic behavior could be described by the first-order kinetic model under different pH. Among all composites, the RG/ZF composite with m RG/ZF = 0.4 showed the best photocatalytic activity under pH = 1. However, the enhanced photocatalytic activity may arise from the effective separation of photogenerated e − -h + pairs and the positive synergetic effect between two components. Moreover, the obtained optimum RG/ZF composite had the saturation magnetization (9.8747 emu/g) enough to make it easy to be separated from solution by means of an external magnetic field. On the other hand, the antibacterial testing implied that the antibacterial properties of composite were depended on the m RG/ZF , and the RG/ZF with m RG/ZF = 0.4 likewise presented the most excellent antibacterial activity, especially to the C. albicans (its IZD and MID was respectively up to 34.5 mm and 12.5 μg/mL). Finally, the possible mechanisms of photocatalysis and antibacterial have been discussed.

In the process of preparing higher manganese silicide (HMS) by magnetron sputtering method, the sputtering base pressure is often a neglected parameter, manganese oxidation is a very difficult problem to avoid. Based on these situations, this paper takes sputtering base pressure as a variable and uses naturally oxidized manganese target as raw material to prepare samples with optimal experimental parameters of HMS, studied the impact of manganese oxidation on the preparation of HMS. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize and analyze the obtained films. It is found that Mn3O4 could be well prepared by MnO and MnO2 on silicon substrate by the same preparation technology to prepare HMS, while control the base pressure higher than 7 × 10−5 Pa. The MnO existence will not cause a negative impact to the production of HMS, but MnO2 should be avoided in any process. When MnO and MnO2 exist at the same time, the sputtering base pressure range of 4 × 10−3–8 × 10−4 Pa should be avoided. The base pressure additionally has a strong regulate effect on the grain size of Mn3O4.

Carbon microspheres with good dispersibility were synthesized by hydrothermal method using glucose as raw material. Taking the as-prepared carbon microsphere as the template, a series of hollow Zn1−x Ni x Fe2O4 spheres (x = 0–1 with interval of 0.2) were prepared by chemical precipitation method. The composition, morphology, electrical and magnetic properties of the hollow Zn1−x Ni x Fe2O4 spheres were characterized. The results of nitrogen adsorption–desorption isotherms indicates that the Zn1−x Ni x Fe2O4 catalyst with different Ni content presents different specific surface area. And the adsorption–photodegradation of samples on rhodamine B and methyl orange solutions were discussed. In addition, the influence of Ni content on material photocatalytic activity has been discussed. These results indicated that the recyclable ZnFe2O4 had a better decontaminating activity than other Zn1−x Ni x Fe2O4 spheres.

The purpose of this study was to develop a method to prepare Metoprolol Succinate (MS) sustained release pellets and compress them into pellet-containing tablets without losing sustained release property. The drug layered pellets were coated with Eudragit NE 30D to obtain a sustained release (SR) property. The mechanical properties and permeability of the coating film were tailored by adjusting the proportion of talc in the coating dispersion and the weight gain of the coating film. Pellets with different MS release rates were tested and then mixed together by different ratios to optimize drug release rate. The mixed pellets were compressed into tablets with cushioning excipients. The results showed that when the ratio of talc and coating material was 1:4, the coating operation could be conducted successfully without pellet conglutination and the mechanical property of the coating film was enhanced to withstand the compress force during tableting. Blending SR-coated pellets of 20% weight gain with SR-coated pellets of 40% weight gain at the ratio of 1:5 could produce a constant and desired drug release rate. The formulation and the procedure developed in the study were suitable to prepare MS pellet-containing tablets with selected SR properties.

A detailed theoretical study of the structural and elastic properties of magnesium silicide Mg2Si under isotropic lattice deformation has been performed based on the first-principles’ pseudopotential method. The results show that isotropic lattice deformation from 94% to 106% results in a linear decrease in the energy gap for the direct Γ15-Γ1 and indirect Γ15-L1 transitions, while the indirect band gap gT15-X1 increases within a range of 94%–104%, and then reduces over the range of 104%. Additionally, isotropic lattice deformation from 94% to 106% also causes a decrease in the elastic constants and modulus of Mg2Si. Furthermore, Mg2Si with lattice deformation from 94% to 106% is brittle, being most brittle at 94% lattice constant.

Magnesium films of various thicknesses were first deposited on silicon (1 1 1) substrates by magnetron sputtering method and then annealed in annealing furnace filled with argon gas. The effects of the magnesium film thickness and the annealing temperature on the formation of Mg2Si films were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Mg2Si thin films thus obtained were found to be polycrystalline and the Mg2Si (2 2 0) orientation is preferred regardless of the magnesium film thickness and annealing temperature. XRD results indicate that high quality magnesium silicide films are produced if the magnesium/silicon samples are annealed at 400 °C for 5 h. Otherwise, the synthesized films annealed at annealing temperatures lower than 350 °C or higher than 450 °C contain magnesium crystallites or magnesium oxide. SEM images have revealed that microstructure grains in the polycrystalline films are about 1–5 μm in dimensions, and the texture of the Mg2Si films becomes denser and more homogeneous as the thickness of the magnesium film increases.

Fe films were deposited on both heated and not-heated Si (100) substrates using direct current magnetron sputtering, and were subsequently annealed by pulsed laser with various laser energy densities. Direct formation of single-phase α-FeSi 2 was confirmed using X-ray diffraction and the surface morphology of films was characterized by scanning electron microscopy. The results show that the crystallinity of the films deposited at room temperature is improved with increasing laser energy densities, while the crystallinity of the films deposited on heated substrates is improved with increasing substrate temperatures. For the samples deposited at the room temperature, the optimal laser energy density for the formation of α-FeSi 2 is 0.95 J cm − 2 .

Semiconducting magnesium silicide (Mg2Si) thin films were synthesized by solid state reaction on Si substrates deposited at various sputtering powers. X-ray diffraction (XRD), Laser confocal Raman microscopy and Scanning electron microscopy (SEM) were used to characterize the crystal structure and surface morphology of the obtained Mg2Si films. XRD and Raman scattering spectra results show the formation of single phase Mg2Si thin films on Si substrates. SEM images show Mg2Si thin films on Si substrates with fine and compact grains were obtained. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A CeO 2 - modified aluminide coating was obtained by composite electro-deposition Ni and CeO 2 particles on 20 steel with different holding time using pack cementation. The growth kinetics curve was given with computer fitting by measuring the thickness of the layer. Scanning electronic microscopy and X-ray energy dispersive spectrometry were used to analyze the microstructure and components of the layer. The results showed that the content of CeO 2 was up to 5.21 wt.% in the rich area of NiAl coatings, which restrain the interdiffusion between the coating and the base during the oxidation process at high temperature. Meanwhile, the growth curve obtained could offer an important basis to forecasting and controlling the depth of the coating.

In this paper, we present the design and fabrication of MEMS hydrophones on a silicon wafer using standard NMOS process technology. The effects of two MOSFET amplifiers with different W/L ratios on the hydrophone performance are investigated. A piezoelectric polymer, polyvinylidene difluoride, is employed as the sensing material. Acoustic impedance possessed by this piezoelectric material provides a reasonable match to that of water, which makes it very attractive for underwater applications. Measurements of the hydrophone devices were carried out in a pulse tube with a frequency range of 4-10 KHz. The results reveal that the hydrophone comprising a MOSFET with larger W/L ratio provides better sensitivity.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Active underwater acoustic cancellation is investigated experimentally in a water‐filled pulse tube using a pressure sensor and a piezo‐composite actuator. The pressure sensor is made of thin 1‐3 piezo‐composite disk encapsulated in acoustic transparent rubber and put right in front of the actuator. A 20‐dB echo reduction to harmonic incident waves in 5–10 kHz is achieved experimentally by directly phase‐shifting the sensor signal and amplifying it to drive the canceling actuator. A robust analog controller is also developed based on the experimentally identified acoustic reflection coefficient of the piezo‐composite transducer with steel backing and the transfer function from piezo‐composite transducer to the pressure sensor. Issues such as robustness and stability of the analog controller are also discussed.

In applications such as ultrasonic immersion testing, damping of flow noise in pipes and ducts and coating of acoustic control surfaces, it is very useful to reduce the reflection of acoustic waves from surfaces. Significant echo reduction can be achieved by addition of an anechoic coating. According to some general design guidelines for a single layer of homogenous coating, a single layer of 15 dB coating must be at least one wavelength thick. For absorbing acoustic waves of low frequencies, inhomogeneities such as metallic fillers, cavities and irregular metallic helices can be introduced into the lossy matrix to substantially enhance the acoustic absorption by acoustic scattering. In this presentation, the acoustic scattering of a single metallic spring embedded in an infinite elastic medium has been investigated using a boundary element formulation. The cross sections of the scattered longitudinal and shear waves have been calculated for various spring sizes, orientations and wave numbers. It will be ...